Making promises we can't keep is a problem.
We do this because we're defensive or insecure in the face of doubt or selling pressure.
We over-promise and inevitably under-deliver - UPOD.
And this destroys any hope of trust - the trust that wasn't there to begin with so we started to exaggerate (and things only got worse).
Now we're the 'used car salesman' and not the one who can solve their problem.